A Chemo-Elastoplastic Analysis of Anisotropic Swelling in an SnO2 Nanowire Under Lithiation

A parametric study is carried out to shed light on the elastoplastic behavior of a nanowire under lithiation. The Li-ion diffusivity is assumed to be significantly higher at near-saturation than at dilute concentration. It leads to the prediction of an Li-ion diffusion jam and consequently a topologically steep step moving along the wire. The analysis shows that the different plastic flow rates due to the different constraint conditions along the longitudinal and radial directions result in apparent anisotropic volume expansion. Either lower yield strength, smaller strain hardening ratio, or higher charging rate would cause greater swelling anisotropy. The numerical results are compared with the experimental observation of an SnO2 nanowire (Huang et al., 2011, “In Situ Observation of the Electrochemical Lithiation of a Single SnO2 Nanowire Electrode,” Science, 330, pp. 1515–1520) to suggest its elastoplastic properties under lithiation.